1. Field of the Invention
The invention relates to a lens hood and an imaging device, and more particularly, to a lens hood and an imaging device that block unnecessary light to be incident on a telephoto lens.
2. Description of the Related Art
When light unnecessary to pick up an image is incident on an imaging lens, the deterioration of the overall contrast, unnecessary light spots, the streak of light, flare, or the like of an image is caused. Accordingly, a cylindrical lens hood is generally mounted on the front end portion of the imaging lens in order to block unnecessary light entering the lens.
“General Form”
The shape of a general lens hood varies according to the angle of view of the imaging lens. From a functional object to block unnecessary light and not to block light necessary to pick up an image, a telephoto lens generally has a simple cylindrical shape but a wide-angle lens or a fisheye lens employs a shape, in which a part of a cylinder is cut out, to satisfy the above-mentioned condition. However, the lens hood in the related art has had a cylindrical shape as a basic shape.
The cylindrical lens hood needs to have a certain length in order to block unnecessary light that is to be incident in an oblique direction by the cylindrical lens hood.
In the case of a telephoto lens, only light, which is incident on the lens at an angle substantially right in front of the lens (an angle within an imaging angle of view) as shown in FIGS. 17A and 17B, is necessary light (an effective light beam). Further, since oblique light, which is incident on the lens at a large angle exceeding the imaging angle of view as shown in FIG. 17C, causes stray light by being reflected in a lens barrel, the oblique light is unnecessary. Accordingly, it is necessary to make the length of a cylindrical lens hood significantly long in order to block unnecessary oblique light, which is less inclined than an effective light beam as shown in FIG. 17D, by a cylindrical lens hood 1.
Since the focal length of a telephoto lens is generally long, a lens barrel tends to be very long. However, since the entire lens unit of a camera is significantly long if the lens hood is also long, it is apparent that it is not preferable that the lens hood is also long.
In the related art, lens hoods, which can be made short and can block unnecessary light not involved with the formation of an image, have been proposed (JP2012-252177A and JP1986-149938A (JP-561-149938A)).
The lens hood disclosed in JP2012-252177A includes: a first hood part that is disposed not to block light flux, which is involved with the formation of an image, of light flux that is incident on the surface of a lens closest to an object in a case in which the lens is opened; and a second hood part that is disposed in the first hood part so as to block a part of light flux involved with the formation of an image. Further, the first hood part and the second hood part are concentrically provided, and an inner wall of the second hood part is disposed substantially in parallel to an optical axis.
JP1986-149938A (JP-561-149938A) discloses lens hoods in which opaque light blocking walls are formed in the shape of a net and which have the shape of a grid, a rectangular shape, a polygonal shape, the shape of a honeycomb, a rhombic shape, and a circular shape in a plan view. Furthermore, JP1986-149938A (JP-561-149938A) discloses a structure in which the sets of cross-sections of the opaque light blocking walls are parallel.